Method and device for evaluating a driving style

ABSTRACT

The invention relates to a method and to a device for evaluating driver performance, comprising the continuous detection of the actual state of travel and the actual traffic situation and determining a reference state of travel pertaining to the actual traffic situation. Said reference state of travel is the state of travel desired in the respective traffic situation according to a predetermined evaluation criterion. According to the invention, the actual state of travel detected is evaluated according to said evaluation criterion by comparing it with the pertaining detected reference state of travel. Subsequently, one or more pieces of feedback information regarding driver performance during a preceding traffic situation are given. The invention also refers to the use of the inventive device for the instructive evaluation of the driver performance of road vehicle users.

BACKGROUND AND SUMMARY OF THE INVENTION

The invention relates to a method and a device for evaluating thedriving style of a driver of a vehicle when travelling on a network oftraffic routes, for example a road network, with a corresponding vehiclesuch as a road vehicle.

Particularly in road traffic, the continuously increasing volume oftraffic is making it difficult to achieve the highest possible level oftraffic safety. In this context, modern traffic telematics are becomingincreasingly significant. With the telematics, the situation or contextin which a vehicle is moving, i.e. both its driving state and thetraffic situation in which it finds itself at a particular time, can bedetected automatically in increasingly better ways by usingvehicle-mounted digital roadmaps in which, in addition to the precisegeometry of the route network, safety-related attributes such aspedestrian crossings, road signs, etc. can also be stored, and by usinghighly precise locating of vehicles and extensive vehicle-mounted sensorsystems.

Such detection of driving states and traffic situations is used, forexample, to detect the driving style of the driver of the vehicle inorder to classify it in a predefined way, such as into a sporty, steadyor economic driving style, etc, and adapt it as a function thereof, forexample transmission shift characteristic curves, or carry outadjustment of the chassis or warn the driver of the vehicle of a currenthazardous situation or directly imminent hazardous situation or againstdriving limiting values being exceeded in a way which endangers drivingsafety.

WO 92/03803 A1 describes a method and a device for evaluating a drivingstyle, in which a desirable driving state is determined as a function ofthe driver behavior and driving state parameters, the driving behaviorof the driver is evaluated and this evaluation is output to the driver.

Such warning systems are customary in a wide range of embodiments. Inone type of such systems, the profile of the road is determinedpredictively in particular with respect to bend geometries andintersection geometries and/or the presence of possible obstacles on theroute in order to warn the driver of the vehicle against approaching thecorresponding hazardous point too quickly, which would endanger safety.The determination of hazardous points in advance can be based here on adigital roadmap, see the Laid-open Application EP 0 819 912 A2, and thePatent EP 0 487 280 B1, or on an image-recording and image-processingsystem which registers the front area of the vehicle, see U.S. Pat. No.5,757,949.

A further type of conventional system uses a digital roadmap which isexpanded with an additional database. The database containstraffic-safety-related information, for example statistical accidentdata from which information about accident blackspots is generated and,for example, output in the form of a voice message (as described in U.S.Pat. No. 5,270,708) or safety zones, such as residential areas, schools,etc. in which the drive power of the vehicle, and thus the possiblespeed, is automatically limited, as disclosed in the Laid-openApplication EP 0 745 965 A1. Or, safety-related information is provided,for example in the form of road signs, which is output visually and/oraudibly as soon as the vehicle approaches the respective location, asdisclosed in U.S. Pat. No. 5,146,219.

A further type of conventional warning system provides for the distancefrom the vehicle travelling ahead to be determined and the driver thento be warned if the distance drops below a predefinable value, see U.S.Pat. No. 5,410,304.

Furthermore, systems which warn against falling asleep and which sensethe movement of the vehicle or the profile of the steering angle anddraw conclusions from these as to the state of the driver in particularwith respect to his degree of tiredness, are known, see European Patentdocument EP 0 049 522 B1 and the German Laid-open Application DE 196 30970 A1.

A general problem of warning systems which warn the driving againstimminent hazardous situations is that the gain in safety which canpossibly be achieved by them is possibly cancelled out again by thedriver through a correspondingly risky driving style as the driver canbe tempted to trust the warning system and try to find out thetriggering limit of the warning system by more risky driving maneuversthan he would make without a warning system, for example to drivethrough a bend so quickly that a bend warning system which is presentresponds. The driver is therefore not particularly stimulated by suchpre-warning systems to subject his driving behavior, under his ownvolition, to specific criteria such as more safe driving with sufficientdistance from the limiting range of the vehicle movement dynamics and/orto drive in a way which is favorable in terms of fuel consumption.

The technical problem on which the invention is based is to provide amethod and a device for evaluating a driving style which can stimulate adriver of a vehicle to select his driving style, i.e. his drivingbehavior, at his own volition in such a way that it fulfils predefinabledesired criteria, for example with respect to driving in a way which issafe for traffic and/or favorable in terms of fuel consumption.

The invention solves this problem by providing a method and a device forevaluating a driving style in which: (a) the current driving state iscontinuously sensed by reference to associated driving state parameters,and the current traffic situation is continuously sensed by reference toassociated traffic situation parameters, (b) an associated referencedriving state which, in the respective traffic situation, represents adriving state which is desirable with respect to a predefinableevaluation criterion, is determined in relation to the respectivelysensed current traffic situation, by using a predefinable trafficsituation reference driving state relation, and (c) the sensed currentdriving state being evaluated by comparison with the respectivelydetermined reference driving state in accordance with the evaluationcriterion, and one or more corresponding acknowledgement informationitems relating to the driving style during a respective precedingtraffic situation being retrospectively output, wherein at least twogroups of acknowledgement information items which are associated withtwo different values of a predefinable category parameter are predefinedas driving style acknowledgement information items which can be output,and an acknowledgement generation criterion is predefined that theamount of acknowledgement information items of the one group which areoutput during a journey remains larger than the amount ofacknowledgement information items of the other group which are output orthe amount of acknowledgement information items of the one group whichare output has a predefinable relationship with that of the other group.

This method and this device characteristically provide foracknowledgement information relating to the driving style during apreceding traffic situation to be output retrospectively, in particularalso as information for the driver of the vehicle relating to how hisdriving behavior during the preceding traffic situation is to beevaluated in accordance with a predefined evaluation criterion. Asevaluation criterion, it is possible in particular to predefine whether,or to what extent, the driving behavior corresponds under the givenconditions to a safe driving style which does not endanger traffic,which includes, in addition to other criteria, a sufficient distancefrom the limiting range of the vehicle movement dynamics. Alternatively,or in addition, other evaluation criteria are possible, for example adriving behavior with the lowest possible fuel consumption.

In order to be able to generate such acknowledgement information, thecurrent driving state and the current traffic situation are continuallysensed, a driving state which fits the current traffic situation, i.e.one that is desirable, in accordance with the predefined evaluationcriterion is derived as a reference driving state and the currentdriving state is evaluated by comparing it with the determined referencedriving state in accordance with the evaluation criterion. In otherwords, it is determined whether, and to what extent, the driving statecorresponds to the reference driving state or how far it departs from itusing the evaluation criterion as a measure of distance. The referencedriving state is not necessarily to be understood here in the context ofevery possible driving state as only a punctual state but ratherdesignates in general an entire range of driving states which, in therespective traffic situation under the predefined evaluation criterion,represent possible setpoint driving states which all fulfil theevaluation criterion equally well. Thus, under the evaluation criterionof a driving behavior which is safe in terms of traffic, the referencedriving state can cover all the driving states which may be classifiedas safe in the respective traffic situation, for example have asufficient distance from the limiting range of the vehicle movementdynamics.

The acknowledgement information provided by the invention which relatesto the driving behavior retrospectively, i.e. relates to therespectively preceding driving behavior, has the fundamental advantageover conventional warning systems which warn of a possible hazardoustraffic situation in advance, that they can form an independentmotivation for the driver of the vehicle to orient his driving behavioraccording to the predefined evaluation criterion, for example to selecta safe and considerate driving style. As a result of suitableconfiguration and selection of the acknowledgement information which isoutput, it is possible for a correct driving behavior which is desirablein terms of the evaluation criterion to be taught by the system, andthus learned by the driver of the vehicle by virtue of the fact that theinformation is configured or selected in such a way that if the currentdriving behavior corresponds essentially to the reference drivingbehavior, then the information positively reinforces the behavior in atargeted fashion. As a result, in most cases it is possible to achieve arelatively larger and longer-lasting change in the driving behavior thanis possible through compulsory measures which act negatively, forexample threats of punishment or confiscation of a driver's license fora certain time, something which is confirmed by corresponding findingsfrom educational psychology.

The method according to the invention and the device according to theinvention contain at least two groups of acknowledgement informationitems of different categories. The outputting of the acknowledgementinformation items is configured in such a way that the amount, i.e. thenumber and/or intensity, of acknowledgement information items of the onegroup which are output, i.e. of the one category, for the respectiveevaluation time period which can comprise the entire respective journeyor part of a respective journey, of one or more traffic situations whichhave been coped with, is kept larger than the amount of acknowledgementinformation items of the other group, or is kept in a predefinablerelationship with the amount for the other group. For example, in thisconfiguration of the invention, positive, “praising” acknowledgements onthe one hand and negative “rebuking” acknowledgements on the other maybe provided, the amount of positive acknowledgements preferably alwaysoutweighing the amount of negative acknowledgements even when theoverall nature of the driving behavior is less positive, and the amountof negative acknowledgements can, if necessary, be reduced to zero, i.e.there are then only positive acknowledgements. As a result, an overallpositive acknowledgement impression for the driver can be produced sothat the acknowledgements do not spoil his pleasure in driving, butrather motivate him selectively to adopt the desired, for example safedriving behavior, and encourages him to define his competence as adriver by safe driving behavior, and not risky driving behavior.

In a method and device which is developed according to a preferredembodiment of the invention, the outputting of driving stylerecommendations is provided, by reference to which recommendations thedriver of the vehicle can orient his driving behavior in such a way thatit corresponds to the reference driving state which is determined forthe respective traffic situation. The driving style recommendations arepreferably selected here in such a way that there is a sufficientdriving behavior margin, in terms of the evaluation criterion of a highlevel of traffic safety, for example the recommended driving style has asufficient safety margin with respect to the limiting range of thevehicle movement dynamics.

A method and device which is developed according to another preferredembodiment of the invention take into account the expected loading onthe driver in the directly imminent traffic situation, i.e. for thedriver travelling along the route directly ahead in the outputting ofinformation for the acknowledgements and the driving stylerecommendations, if they are provided, the state of the route beingestimated in advance for this purpose and in order to sense the currenttraffic situation. The information is then output only in time periodsin which the driver is not too heavily loaded with the imminent drivingtasks so that he can pay sufficient attention to the information itemswhich are output.

One advantageous embodiment of the invention is illustrated in thedrawing and will be described below.

BRIEF DESCRIPTION OF THE DRAWING

The single FIGURE shows a block diagram of a method and a device forevaluating a driving style with evaluating driving style acknowledgementinformation items.

DETAILED DESCRIPTION OF THE DRAWING

The FIGURE is a block diagram of a device for evaluating a driving style(having the components of interest here), showing the functionalinteraction of the components. At the same time, the figure constitutesa flowchart showing the sequence of the driving style evaluation methodwhich is carried out by this device if the individual blocks of theblock diagram are not considered as system components in this respect,but rather as method steps which are carried out by the respectivesystem components. For this reason, the individual system components andthe functions carried out by them will be explained below in parallel.

A sensor block 1 comprises the sensor system which is necessary forsensing the position and the movement state of the vehicle. In order toimplement such a sensor system, the person skilled in the art can makeuse of conventional sensor systems in order to fulfill this purpose,which requires no further explanation here. The sensor system 1 canoptionally comprise sensor elements for sensing the state of operatorcontrols which are actuated by the driver, the state of the routenetwork, i.e. the state of the road in the case of road vehicles, thevisibility and the entire context of the vehicle in terms of traffic.

The profile of the route, the category of the route, for examplemotorway, country road or road within a built-up area, and the number oftraffic lanes, as well as preferably further safety-related attributessuch as pedestrian crossings, priority regulations and speed limits, arestored in a digital roadmap 2 of a customary type.

The vehicle's own system can communicate with other vehicles, with atraffic information control center and/or with other communicationsinfrastructure components, by using an optional communications platform3 of a customary design.

The current state of the vehicle, road and surroundings are determinedin a state-determining unit 4. Specifically, the state-determining unit4 calculates the current position and the movement state of the vehiclefrom the data which is called for that purpose from the respectivesensors of the sensor block 1 and from the digital roadmap 2. When thereis additional use of data transferred via the communications platform 3and of data from the above-mentioned optional sensor elements, it ispossible, when necessary, to determine the state of the vehicle, roadand surroundings with improved precision, for example the coefficient offriction of the surface of the road, the visibility, the distance fromthe vehicle travelling ahead and/or information can also be included inthe determination of the state.

A route prediction unit 5 is used to estimate in advance the futureprofile of the route and the future properties of the route for apredefinable prediction time period by using the current position of thevehicle determined by the state-determining unit 4 and by using the dataof the digital roadmap 2. The prediction of the future profile of theroute comprises, in particular, the qualitative and quantitativeestimation in advance of imminent bends. Future properties of the routeare, for example, imminent speed limits and intersections withrespective priority regulations.

The route preview data generated by the route prediction unit 5 areused, in a driver-loading prediction unit 7, to estimate in advance theexpected loading, i.e. work demanded of the driver of the vehicle,involved in carrying out the imminent driving task, and to determinethose time windows in which the predicted work demanded of the driver isbelow a predefinable threshold so that the time windows are thereforeparticularly suitable for the outputting of information to the driver.

A traffic situation-determining unit 6 determines the current trafficsituation by reference to the route preview data of the route predictionunit 5 and by reference to the state data supplied by thestate-determining unit 4. In this way, the traffic situation-determiningunit 6 can, for example, detect automatically when the vehicle isapproaching a traffic light-controlled intersection in thick fog as sucha traffic situation. The same applies to all other traffic situationswhich typically occur in traffic. The means and algorithms which arenecessary for this are known to the person skilled in the prior art andtherefore need no further description here.

For the current traffic situation which is determined by using thetraffic situation-determining unit 6, a reference-determining unit 8determines an associated reference driving state which is adapted to thetraffic situation. The process comprises the determination of adaptedvalues for the vehicle speed, the positive or negative vehicleacceleration, the longitudinal distance from a vehicle travelling ahead,the possible activation of an indicator light, etc. This referencedriving state, also referred to below as reference driving behavior, isselected in such a way that in the given traffic situation it satisfiesa predefined evaluation criterion, for example the criterion of safedriving behavior in order to achieve a high level of traffic safety. Inthis context, the reference driving state may not only designate apunctual state but also an entire range of the state space of possibledriving states. It is selected in such a way that it guaranteessufficient margins, i.e. sufficient safety margins in the case of thecriterion of a high level of traffic safety, so that relatively smalldeviations from this reference driving behavior still do not lead to adriving state which is undesired, for example critical in terms ofsafety. The reference driving state which is determined in this way isstored, on the one hand, in a buffer 9, which can be deleted again afterthe end of the evaluation operation. On the other hand, the referencedriving state data is used by a recommendation-generating unit 10 togenerate driving recommendations corresponding to the determinedreference driving state and to supply them to an output unit 11. Thelatter comprises one or more output devices with which the informationitems which are input can be conveyed to the driver in a perceptiblefashion, for example visually, haptically and/or audibly. For example,such a driving recommendation can contain the information that aspecific maximum cornering speed is recommended to travel through animminent bend. As the name suggests, the emphasis is on therecommendation aspect of this information and not for example on itswarning aspect.

In parallel with the determination of the respective reference drivingstate by the reference-determining unit 8, a driving state-determiningunit 12 continuously determines the current driving state, i.e. thecurrent driving behavior, also referred to as driver behavior, byreference to the necessary input data which is supplied to it for thispurpose by the state-determining unit 4. In this context, the currentdriving behavior which is determined by the driving state-determiningunit 12 is described by the same driving state parameters as thereference driving behavior determined by the reference-determining unit8. The current-driving state data which is generated in this way by thedriving state-determining unit 12 is also stored in the buffer 9.

The data which relates to the current traffic situation and which isgenerated by the traffic situation-determining unit 6 is used, by asituation change-detection unit 13, to detect a change in the currenttraffic situation, i.e. the entirety of all the possible trafficsituations which occur are discretized into a finite number of differentsituations, and a transition from one of these discretized trafficsituations to another is detected. If the situation change-detectingunit 13 detects such a change in the traffic situation, it reports thisto a driving state-evaluation unit 14. This then evaluates the drivingbehavior in the traffic situation driven through last.

For this purpose, the driving state-evaluation unit 14 reads out thestored data relating to this in the buffer 9 and compares the actualrecorded driving behavior with the reference behavior which was recordedin parallel. This evaluation is carried out according to drivingstyle-evaluation criteria which the person skilled in the art isfamiliar with for this purpose. In the example of the evaluationcriterion of a high level of traffic safety, the evaluation contains,for example, in particular the determination of whether the actualdriving behavior was in the range which was noncritical in terms of thevehicle movement dynamics or else had reached the limiting range of thevehicle movement dynamics. The comparison result, i.e. the evaluatedtraffic situation, is stored in an associated evaluation data memory 15,also referred to as situation memory. Data which is no longer requiredin the buffer 9 can then be deleted.

The evaluation which is performed by the evaluation unit 14 includeshere in particular a coarse distinction between whether the actualdriving state has corresponded to the reference state at least to acertain degree, or whether it differs markedly from it, i.e. whether adriving behavior which is still tolerable overall or whether a drivingbehavior which is rather no longer tolerable, has occurred. Depending onrequirements, finer gradation of the evaluation of the driving style maybe provided. The evaluation result is supplied to an acknowledgementunit 16 and enables the acknowledgement unit 16 to generate differentacknowledgements which can be roughly classified as positive, “praising”acknowledgements on the one hand and negative, “criticizing”acknowledgements on the other, in which case finer gradations are alsopossible here depending on requirements. The individual acknowledgementsare preferably combined by the acknowledgement unit 16 in such a waythat the amount of positive acknowledgements outweighs that of negativeacknowledgements or is kept to a specific relation to the amount so thata desired overall positive impression of the acknowledgement informationduring a journey is produced, and maintained, for the driver. As aresult, the readiness of the driver of the vehicle to behave inaccordance with the evaluation criterion is reinforced in a targetedfashion.

The acknowledgement unit 16 generates the evaluating acknowledgementsrelating to the driving style in the preceding traffic situation orsituations during a respective journey and/or after the end of thejourney. To do this, it reads the data generated by the drivingstate-evaluation unit 14 and stored in the situation memory 15 out ofsaid memory 15, subjects this data to a suitable statistical evaluationand, if appropriate, combines a plurality of individual acknowledgementsto form an acknowledgement information item which is to be output. Thisis preferably carried out in such a way that at least one individualacknowledgement of the positive category is contained in eachacknowledgement information item to be output, and/or the number or thestrength of individual acknowledgements of the positive category isgreater for each evaluated traffic situation or at least for relativelylong evaluation time periods than that of the individual acknowledgementof the criticizing category, or is kept to a specific relation to them.

The acknowledgement unit 16 outputs the generated acknowledgementinformation items to the output unit 11 only in the time periods inwhich the work involved for the driver in carrying out the imminentdriving task, as predicted by the driver-loading prediction unit 7, isnot above the aforesaid threshold so that it is also actually possiblefor the driver of the vehicle to absorb the acknowledgement information.According to this secondary condition, the driving style-evaluatingacknowledgement is either provided continuously by the acknowledgementunit 16, such as after every occurrence of an evaluated trafficsituation with driving behavior which is assessed as being safe orcritical, or is provided intermittently. Intermittent acknowledgementscan be generated with suitable reinforcement, for example by a quotareinforcement, which makes the strength of acknowledgements dependent onthe frequency of the occurrence of the associated driving style, or bymeans of a time interval reinforcement, which makes the strength of theacknowledgement dependent on the time which has passed since the lastacknowledgement. With both types of acknowledgement, the outputting ofthe acknowledgements can take place at fixed time intervals, for exampleevery 5 minutes, or at variable time intervals, for example once every 3minutes and the other every 7 minutes. The output unit 11 conveys theacknowledgement information items in a suitable way, for examplevisually, audibly and/or haptically.

As the description above of an advantageous exemplary embodiment shows,the invention makes available a method and a device for evaluating adriving style, which are distinguished by driving style-evaluationacknowledgement information items which are output retrospectively andwith which the driver of the vehicle can be motivated to adopt, by hisown free will, a desirable driving behavior in a targeted fashion. Theaspect of free will increases the degree of acceptance of the system.

If necessary, the driving-style evaluation in the form ofacknowledgements can be expanded to the effect that there are directpersonal advantages for the driver of the vehicle in the case ofpositive evaluation results. Thus, there may be provision that bonuspoints or credits are awarded for positive evaluation results and theseare stored, for example on a chip card, so that the driver can cash themin, for example at the next customer service stop, in certain shops orat cultural events. Alternatively, or in addition, free units for amobile telephone may be awarded for positive evaluation results, orcontributions to vehicle insurance or rebates on said insurance may bemade dependent on the acknowledged driving style-evaluation results.

In addition to the evaluation criterion, mentioned as having priorityabove, of achieving a high level of traffic safety, the invention is, ofcourse, also suitable for alternative or additional evaluation criteria.In particular for professional drivers who do a large amount of driving,a useful evaluation criterion can be, for example, achieving a drivingstyle with the lowest possible consumption, which is to be aimed forwhile taking into account economic and ecological aspects.

1. A method for evaluating a driving style, the method comprising theacts of: continuously sensing a current driving state by reference toassociated driving state parameters and continuously sensing a currenttraffic situation by reference to associated traffic situationparameters; determining an associated reference driving state inrelation to a respectively sensed current traffic situation using apredefinable traffic situation reference driving state relation, theassociated reference driving state representing a desirable drivingstate in a respective traffic situation with respect to a predefinableevaluation criterion; evaluating the sensed current driving state bycomparison with the respectively associated reference driving state inaccordance with the predefinable evaluation criterion; outputting one ormore acknowledgment information items relating to a driving style duringa respective preceding traffic situation, wherein at least two groups ofthe acknowledgement information items associated with two differentvalues of a predefinable category parameter are predefined as drivingstyle acknowledgement information items available for output; andwherein an acknowledgment generation criterion is predefined such thatan amount of acknowledgment information items of one of the two groupsoutput during a journey remains larger than an amount of acknowledgmentinformation items of another of the two groups which are output, or anamount of acknowledgment information items of the one group which areoutput has a predefinable relationship with that of the other group. 2.The method according to claim 1, further comprising the act ofoutputting driving style recommendations as a function of the referencedriving state determined in relation to the current traffic situation.3. The method according to claim 2, wherein the act of continuouslysensing the current traffic situation comprises the act of using a routestate prediction to sense the current traffic situation, the route stateprediction being also used to estimate in advance an expected loading onthe driver; and wherein the outputting of the acknowledgment informationitems or driving style recommendations occurs only in time periods inwhich the expected loading on the driver is below a predefinablethreshold.
 4. The method according to claim 1, wherein the act ofcontinuously sensing the current traffic situation comprises the act ofusing a route state prediction to sense the current traffic situation,the route state prediction being also used to estimate in advance anexpected loading on the driver; and wherein the act of outputting theacknowledgment information items only occurs in time periods in whichthe expected loading on the driver is below a predefinable threshold. 5.A device for evaluating a driving style, comprising: means forcontinuously sensing a current driving state by reference to associateddriving state parameters and a current traffic situation by reference toassociated traffic situation parameters; a reference determining unitfor determining a reference driving state associated with the sensedcurrent traffic situation, the reference driving state representing adesirable driving state in a respective traffic situation in accordancewith a predefinable evaluation criterion; a driving state-evaluationunit for evaluating the sensed current driving state by comparison witha respectively determined reference driving state in accordance with theevaluation criterion; an acknowledgement unit for outputting one or morecorresponding acknowledgment information items relating to a drivingstyle during a preceding traffic situation; wherein the driving stateevaluation unit generates acknowledgements of at least two differentcategories and matches an output of acknowledgement information itemssuch that an amount of the acknowledgement information items of onegroup output during a journey remains larger than an amount ofacknowledgement information items of another group output in acorresponding time period.
 6. A device according to claim 5, furthercomprising: a recommendation generating unit for generating andoutputting driving style recommendations as a function of the referencedriving state respectively determined in relation to the current trafficsituation.
 7. A device according to claim 6, further comprising: a routestate prediction unit and a driver-loading prediction unit, the driverloading prediction unit using route state estimation data from the routestate prediction unit for estimating in advance an expected loading onthe driver for the current traffic situation; and wherein theacknowledgment unit and the recommendation-generating unit outputs theacknowledgment information items and the driving style recommendationsonly in time periods in which the expected loading on the driver isbelow a predefinable threshold, or the acknowledgment unit outputs theacknowledgment information items only in time periods in which theexpected loading on the driver is below a predefinable threshold, or therecommendation-generating unit outputs the driving style recommendationsonly in time periods in which the expected loading on the driver isbelow a predefinable threshold.
 8. A device according to claim 5,further comprising: a route state prediction unit and a driver-loadingprediction unit, the driver loading prediction unit using route stateestimation data from the route state prediction unit for estimating inadvance an expected loading on the driver for the current trafficsituation; and wherein the acknowledgment unit outputs theacknowledgment information items only in time periods in which theexpected loading on the driver is below a predefinable threshold.
 9. Amethod of providing feedback on a driving style of a driver of avehicle, the method comprising the acts of: categorizing at least twogroups of driving style acknowledgment information items, said twogroups being associated with different values of a predefinable categoryparameter; and predefining an acknowledgment generation criterion suchthat an amount of driving style acknowledgment information items of onegroup output during a journey remains larger than an amount of drivingstyle acknowledgment information items of another group output in acorresponding time period; and feeding back to the driver the drivingstyle acknowledgment information items based on the predefined drivingstyle acknowledgment generation criterion for a preceding trafficsituation.
 10. The method according to claim 9, further comprising theact of prohibiting feedback of the driving style acknowledgmentinformation items during time periods in which an expected load on thedriver is above a predefined threshold.